Therapeutic indications of alpha-2 adrenoceptor agonists have been discussed in the literature: Ruffolo, R. R., A. J. Nichols, J. M. Stadel, & J. P. Hieble, "Pharmacologic and Therapeutic Applications of Alpha-2 Adrenoceptor Subtypes", Annual Review of Pharmacology & Toxicology, Vol. 32 (1993) pp. 243-279.
Information regarding alpha adrenergic receptors, agonists and antagonists, in general, and regarding compounds related in structure to those of this invention are disclosed in the following references: Timmermans, P. B. M. W. M., A. T. Chiu & M. J. M. C. Thoolen, "12.1 .alpha.-Adrenergic Receptors", Comprehensive Medicinal Chemistry, Vol. 3, Membranes & Receptors, P. G. Sammes & J. B. Taylor, eds., Pergamon Press (1990), pp. 133-185; Timmermans, P. B. M. W. M. & P. A. van Zwieten, ".alpha.-Adrenoceptor Agonists and Antagonists", Drugs of the Future, Vol. 9, No. 1, (January, 1984), pp. 41-55; Megens, A. A. H. P., J. E. Leysen, F. H. L. Awouters & C. J. E. Niemegeers, "Further Validation of in vivo and in vitro Pharmacological Procedures for Assessing the .alpha..sub.1 and .alpha..sub.2 -Selectivity of Test Compounds: (2) .alpha.-Adrenoceptor Agonists", European Journal of Pharmacology, Vol. 129 (1986), pp. 57-64; Timmermans, P. B. M. W. M., A. de Jonge, M. J. M. C. Thoolen, B. Wilffert, H. Batink & P. A. van Zwieten, "Quantitative Relationships between .alpha.-Adrenergic Activity and Binding Affinity of .alpha.-Adrenoceptor Agonists and Antagonists", Journal of Medicinal Chemistry, Vol. 27 (1984) pp. 495-503; van Meel, J. C. A., A. de Jonge, P. B. M. W. M. Timmermans & P. A. van Zwieten, "Selectivity of Some Alpha Adrenoceptor Agonists for Peripheral Alpha-1 and Alpha-2 Adrenoceptors in the Normotensive Rat", The Journal of Pharmacolocy and Experimental Therapeutics, Vol. 219, No. 3 (1981), pp. 760-767; Chapleo, C. B., J. C. Doxey, P. L. Myers, M. Myers, C. F. C. Smith & M. R. Stillings, "Effect of 1,4-Dioxanyl Substitution on the Adrenergic Activity of Some Standard .alpha.-Adrenoreceptor Agents", European Journal of Medicinal Chemistry, Vol. 24 (1989), pp. 619-622; Chapieo, C. B., R. C. M. Butler, D. C. England, P. L. Myers, A. G. Roach, C. F. C. Smith, M. R. Stillings & I. F. Tulloch, "Heteroaromatic Analogues of the .alpha..sub.2 -Adrenoreceptor Partial Agonist Clonidine", Journal of Medicinal Chemistry, Vol. 32 (1989), pp. 1627-1630; Clare, K. A., M. C. Scrutton & N. T. Thompson, "Effects of .alpha..sub.2 -Adrenoceptor Agonists and of Related Compounds on Aggregation of, and on Adenylate Cyclase Activity in, Human Platelets", British Journal of Pharmacology, Vol. 82 (1984), pp. 467-476; U. S. Pat. No. 3,890,319 issued to Danielewicz, Snarey & Thomas on Jun. 17, 1975; and U. S. Pat. No. 5,091,528 issued to Gluchowski on Feb. 25, 1992. However, many compounds related in structure to those of this invention do not provide the activity and specificity desirable when treating disorders modulated by alpha-2 adrenoceptors.
For example, many compounds found to be effective nasal decongestants are frequently found to have undesirable side effects, such as causing hypertension and insomnia at systemically effective doses. There is a need for new drugs which provide relief from nasal congestion without causing these undesirable side effects.